var code ; //在全局 定义验证码
function createCode(){
    code = "";
    var codeLength = 4;//验证码的长度
    var checkCode = document.getElementById("checkCode");
    checkCode.value = "";
    var selectChar = new Array(1,2,3,4,5,6,7,8,9,'a','b','c','d','e','f','g','h','j','k','l','m','n','p','q','r','s','t','u','v','w','x','y','z','A','B','C','D','E','F','G','H','J','K','L','M','N','P','Q','R','S','T','U','V','W','X','Y','Z');

    for(var i=0;i<codeLength;i++) {
        var charIndex = Math.floor(Math.random()*60);
        code +=selectChar[charIndex];
    }
    if(code.length != codeLength){
        createCode();
    }
    checkCode.value = code;
}


function validate () {
    var inputCode = document.getElementById("input1").value.toUpperCase();
    var codeToUp = code.toUpperCase();
    if (inputCode.length <= 0) {
        alert("请输入验证码！");
        return false;
    }
    else if (inputCode != codeToUp) {
        alert("验证码输入错误！");
        createCode();
        return false;
    }
    else {
        // alert("输入正确，输入的验证码为：" + inputCode);
        return true;
    }
}